The biggest argument is the other coin networks that have been running for years in production without proof of work. Nano and EOS have interesting consensus models. Nano manages to remove all inflation and transaction fees and is just a base level currency. EOS has an account fee and you have to rent resources but can do code execution on transactions (smart contracts). They both rely on accounts voting for representatives and have had similar problems with spam. Nano has been running for > 4 years and EOS for > 1 years.